1. Field of the Invention
The present invention relates to a fluid supply valve. More particularly, the present invention is concerned with a fluid supply valve which is well suited as an ink tank valve particularly in an ink jet recording apparatus for the purpose of favorably supplying a recording head portion from an ink chamber with an ink in an amount corresponding to the amount of an ink which is discharged from said recording head portion at the time of recording.
2. Description of the Related Arts
An ink jet recording apparatus has heretofore been equipped with an ink tank which has an ink chamber to be filled in with an ink and also an ink supply portion which supplies a recording head portion with an ink. Examples of types of the ink tanks include a type which is constituted so that an ink is supplied to a recording head which is stationarily attached to a carriage, through tubes arranged everywhere in an ink jet recording apparatus, and an ink tank is freely attachable to and detachable from said apparatus; a type in which an ink tank is constituted integrally with a recording head, and the resultant integrated unit is freely attachable to and detachable from a carriage; and the like types.
In the former type of the ink tank, an ink is supplied to the recording head by providing a water head difference therebetween, while in the latter type, an ink is supplied to the recording head by providing the ink tank with a negative pressure generation source.
There have frequently been proposed in recent years, the ink jet recording apparatuses which adopt the latter type of the ink tank from the viewpoints of miniaturizing the apparatuses as well as the easiness of maintenance work.
Such an ink tank is required to be capable of favorably supplying an ink in an amount corresponding to the amount of the ink discharged from the recording head at the time of recording, and also to be free from the leakage of an ink through a discharge port at the time of nonrecording.
There is available for example, as an ink tank meeting the above-mentioned requirements, an ink tank in the form of cartridge which is freely attachable to and detachable from a carriage, and in which a recording head is integrated with an ink tank, and an absorbent (foam) is filled inside the ink tank. It is made possible by such an absorbent filled in an ink tank to maintain the ink meniscus at an stable level at the ink discharge portion of the recording head, and at the same time it is made possible by the capillary power of the absorbent to properly preserve the ink in the ink tank. In this case, it is needed that almost entire inside of the ink tank be filled in with the absorbent. Thus by allowing the absorbent to preserve an amount of ink a slightly less than the maximum preservable amount thereof, the capillary power of the absorbent is utilized to generate a negative internal pressure. It is therefore, made possible to minimize the amount of the ink leaking through the discharge portion of the recording head and through the ink tank portion communicating with the atmosphere, even in the case where a mechanical shock such as vibration or a thermal shock such as temperature variation is applied to the recording head and the ink tank.
The aforesaid method in which the ink tank inside is almost entirely filled with an absorbent involves the problems that the negative pressure of the absorbent increases accompanying the consumption of the ink, and increases the amount of the ink remaining in the ink tank without being supplied to the recording head, thereby bringing about a low utilization efficiency of the ink.
In order to solve such problems, there is proposed, for example, a cartridge for an ink jet recording head which cartridge is constituted so that an ink reservoir is separated from a cavity by a wall equipped with a communication opening on the lower side of an ink tank, and an umbrella check valve is installed movably in the communication opening so as to discharge the ink in the ink reservoir into the cavity by opening itself at the point of time when the ink pressure in the ink jet recording head is lowered, whereby the ink is supplied to the ink-jet recording head [refer to Japanese Patent Application Laid Open No. 231759/1987 Sho-62)].
According to the above mentioned constitution it is made unnecessary to accommodate an absorbent in the cartridge, thereby enabling to enlarge the substantial accommodation capacity of the ink tank. In general, however, a serious problem with the aforesaid constitution remains unsolved in that the umbrella check valve has an offset value which is too high to precisely regulate the amount of the ink to be supplied to the recording head, thus bringing about unfavorable variation in the amount of the ink to be supplied and consequent deterioration of the quality of the printed letters.
There are also problems that in the state of the umbrella check valve being opened, the recording head is completely isolated from the ink reservoir, which increases the pressure in the cavity, destroys the seal at the connection to the recording head, and thereby causes ink leakage when the ink in the cavity is volumetrically expanded by 2 to 5%, approx. owing to the variation in the environmental temperature; and that in the state of the ink tank being mounted on the recording head, the increased pressure as mentioned above is applied as such to the recording head, which makes it impossible to maintain a negative pressure between the recording head and the ink tank, and thereby causes ink leakage through the recording head.
There is further a problem that since the umbrella check valve is not imparted with a sufficient valve opening power by several tens millimeter of water column that is to be maintained for the purpose of stably supplying the recording head with the ink, there is a fear that the valve is opened in response to the swing of the ink caused by the movement of a carriage, thereby bringing about inferior stability of the printed letters.
In order to solve the foregoing problems involved in such an umbrella check valve in such circumstances, an attempt is made, for example, to employ an ink tank valve which is installed at the position dividing an ink chamber and an ink supply portion, is moved by the difference in pressure between the ink chamber and the ink supply portion, and supplies the recording head with the ink filled in the ink chamber.
By equipping the ink tank with such an ink tank valve, it is made possible to certainly supply the recording head with the ink, by surely responding to the slight difference in pressure between the ink tank and the recording head without being influenced by the swing of the ink due to the movement of the carriage, while maintaining the negative pressure well suited for printing between the recording head and a recording medium. It is further made possible thereby to prevent the ink from leaking by variation in temperature through the ink supply port or through the recording head.
As the structure of the ink tank valve which is installed at the position dividing the ink chamber and the ink supply portion, there have been proposed a variety of structures, of which the structures as shown in FIGS. 1 and 2, respectively are preferably exemplified.
FIG. 1 is a cross sectional view showing one example of an ink tank valve, while FIG. 2 is a partially cross sectional view showing one example of a disc shaped valve body to be used in said ink tank valve. The ink tank valve C is installed at the position dividing the ink chamber A and the ink supply portion B. The disc shaped valve body 1 to be used in the ink tank valve C is constituted of a disc shaped elastic material which has an ink supply port 3 in the central part thereof and the peripheral portion of which is reinforced with and fixed to a rigid material such as polypropylene. The aforesaid disc shaped valve body 1 is supported by a movable support 5 equipped with a spring 6, and abuts against a fixed valve seat 4 at the time of non recording, while the ink tank valve C is in the closed state. Since the ink in the ink supply portion B is supplied to the recording head portion at the time of recording, the ink therein is decreased to cause negative pressure therein. In consequence, the movable support 5 moves towards the compression direction of the spring, and thus the disc shaped valve body 1 is separated from the fixed valve seat 4 and brings the ink tank valve C to an opened state, whereby the ink in the ink chamber A is supplied to the ink supply portion B through the ink supply port 3. When the negative pressure in the ink supply portion B is eliminated thereby, the disc shaped valve body 1 again abuts against the fixed valve seat 4 by the action of the movable support 5, and thus stops the supply of ink to the ink supply portion B.
It is important with regard to the ink tank valve having such a structure that the ink tank valve be capable at the time of recording, of supplying an ink in an amount corresponding to the amount of the ink that is discharged from the recording head. In order to meet the above mentioned requirement, it is desirable to weaken the reaction force in the case of the deformation of the disc shaped valve body to be used in the ink tank valve. However, the disc-shaped valve body to be used in a conventional ink tank valve, which usually has the structure as shown in FIG. 2, and a wall thickness of 0.4 mm, approximately, has involved such problems that the reaction force is not necessarily weak in the case of the deformation of the disc shaped valve body and at the same time, the supply of the ink can not sufficiently follow the amount of the ink which is discharged from the recording head, and the like problems.
Under such circumstances, a general object of the present invention is to provide a fluid supply valve which is well suited as an ink tank valve particularly in an ink jet recording apparatus for the purpose of favorably supplying a recording head portion from an ink chamber with an ink in an amount corresponding to the amount of an ink which is discharged from said recording head portion at the time of recording.
Other objects of the present invention will be obvious from the contents of this specification hereinafter disclosed.
As a result of intensive research and investigation accumulated by the present inventors in order to achieve the above-mentioned objects, it has been found that the reaction force at the time of the deformation of a disc shaped valve body is weakened by the use of a disc shaped valve body in which the thickness or the intermediate annular portion between the liquid supply port and the peripheral portion is non-uniformized in the radial direction as compared with a conventional valve body in which the thickness thereof is uniformized in the radial direction, and that the fluid supply valve using the former disc shaped valve body can conform to the above mentioned objects of the present invention.
In addition, it has been found that the reaction force at the time of the deformation of a disc shaped valve body is weakened by the use of a disc-shaped valve body which is equipped with at least one inflectional portion in the radial direction between the liquid supply port and the peripheral portion as compared with a conventional valve body which is not equipped with any inflectional portion in the radial direction, and that the fluid feed valve using the former disc-shaped valve body can conform to the above mentioned objects of the present invention. The present invention has been accomplished by the foregoing findings and information.
Specifically, the present invention provides a fluid supply valve comprising a disc-shaped valve body which is equipped with a fluid supply port in the central portion thereof and composed of an elastic material whose peripheral portion is reinforced and fixed with a rigid material, said fluid supply port being closed when said valve body abuts against a fixed valve seat placed so as to be opposite to said fluid supply port, and being opened when said valve body is separated from said fixed valve seat, wherein the thickness of the intermediate annular portion between the liquid supply port and the peripheral portion in said valve body is non uniformized in the radial direction.
Moreover, the present invention provides a fluid supply valve comprising a disc shaped valve body which is equipped with a fluid supply port in the central portion thereof and composed of an elastic material whose peripheral portion is reinforced and fixed with a rigid material, said fluid supply port being closed when said valve body abuts against a fixed valve seat placed so as to be opposite to said fluid supply port, and being opened when said valve body is separated from said fixed valve seat, wherein said valve body is equipped with at least one inflectional portion in the radial direction between the liquid supply port and the peripheral portion in said valve body